Draft control means for fuel burners



Aug. 7, 1956 R- D. REED ET AL 2,757,721

DRAFT CONTROL MEANS FOR FUEL BURNERS Fild June 9, 1952 INVENTORE QfRM ATTORNEY United States Patent DRAFT CONTROL MEANS FOR FUEL BURNERS Robert D. Reed and John S. Zink, Tulsa, Okla., assignors,

.by direct and inesne assignments, to John Zink Company, Tulsa, Okla, a corporation of Delaware Application June 9, 1952, Serial No. 22,4*36

2 Claims. (Cl. 158-15) The present invention relates to a mechanism serving as an air register for controlling the movement of air admitted to the presence of a fuel burner and more particularly pertains to improvements in such devices for maintaining a substantially constant air pressure drop for a given volume of air regardless of the extent of rotation imparted to the air.

t is known in the combustion art to impart a whirling movement to air as it moves into the presence of the fuel being burned. In some types of combustion the second ary air stream must be carefully controlled with respect to rotation or the lack of rotation in the presence of the fuel being burned and in accordance with the requirement of the fuel being consumed. Spinning of the secondary air serves several purposes. The whirling air increases the condition of turbulence for mixture of fuel and air. As the speed of rotation of the secondary air is increased the tangential component is increased causing the air to move radially and thus shortening and widening the flame. As the spin of the air stream is decreased the flame becomes more elongated axially from the burner. The control of the rotation of the secondary air is highly desirable in a number of burner installations.

The prior art includes arrangements for controlling the degree of rotation and such whirling movement is in one type provided by means of tiltable louvers at the periphery of the burner opening. The air flowing over the tiltable louvers is diverted into a tangential direction in dependence upon the angle of inclination of the louvers. Such a prior arrangement has the disadvantage-of providing a marked increase in pressure drop of the air for a given volume because the tilted louvers reduce the cross sectional area for admission of the secondary air. The tilted louvers of such devices render it impossible to maintain a substantially constant air pressure drop across the register as the rotation of the secondary air stream is adjusted.

An object of the present invention is to provide an air register mechanism for controlling the rotation or lack of rotation of the secondary air stream and to maintain a relatively constant pressure drop for a given volume of air delivered to the burner regardless of the degree or extent of rotation imparted to the entering air stream.

Another object of the invention is to provide control means for imparting rotational movement to the secondary air entering into the presence of fuel being consumed by a burner Without adjusting the angular disposition of louvers and such results are accomplished by diverting variable portions of a given volume of air over different lengths of vanes having fixed angular positions.

A still further object of the invention is to provide a mechanism for controlling the admission of air for ture with fuel being burned so constructed as to be capable of diverting variable portions of a given volume of air over different lengths of vanes having fixed angular positions with a remainder of the given volume of air entering through an area in which there are no vanes so that one portion of the given volume of air is caused to spin rapidly while no spin is imparted to the other portion of the air "ice flowing through the area in which there are no vanes to provide two separate streams of air, one having a maximum of spin and one devoid of rotational movement with the two streams combining enroute to the zone for mixture with the fuel.

Other objects and features of the invention will be appreciated and become apparent to those skilled in the art as the present disclosure proceeds and upon consideration of the following detailed description taken in connection with the accompanying drawing wherein an embodiment of the invention is disclosed.

In the drawing:

Fig. 1 is a front elevational view of an air register assembly embodying the invention.

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary sectional view taken on the line 3-3 of Fig. 2.

Fig. 4- is a perspective view on a smaller scale showing the ring-shaped baflle and the actuating handles therefor.

Fig. 5 is a sectional view on a reduced scale taken on the line 5-5 of Fig. 2 and showing the air shutter in elevation.

Fig. 6 is a diagrammatic view illustrating the flame when no spin is imparted to the incoming air.

Fig. 7 is a similar diagrammatic view showing the approximate shape of the flame when rotation is imparted to the secondary air.

In carrying out the invention the air control mechanism is illustrated in association with a furnace which may be of any suitable type having an insulated wall represented at 10 covered with sheet metal as shown at 11 in a conventional manner. opening at 12 for receiving a contoured sleeve 14 formed of suitable refractory material. The covering metal 11 is likewise provided with an opening 16 in general registering with the opening 12. A relatively large aperture is thereby provided in the furnace wall through which the flame from a burner diagrammatically indicated at 17 is projected. The invention has utility in connection with burners for various types of fuel such as an oil, gas or pulverized solid fuel or combinations of such combustible materials.

The control mechanism for the secondary air includes av other parts of the air register structure are supported as hereinafter described.

An annular member 22 is provided spaced outwardly of the flange 21.

any desired manner. The vanes 23 slope with respect to true radial planes and are disposed in chord positions as will be evident upon consideration of Fig. 3. The vanes 23 are disposed in equally circumferentially spaced relationship around the annular member 22. The ends 26 of the vanes abut against the inturned flange 21 of the mounting ring 18. The vanes may be secured to'the flange 21 if desired.

A ring-shaped front plate 27 is maintained in spaced relationship outwardly of the annular member 22 by means of spacer elements 28. These tubular spacer elements engage the annular member 22 at their inner ends and the front plate 27 abuts against the outerends of the spacer elements 28. A plurality of. bolts 29 extend through the front plate 27 and through the spacer sleeves 28 and through openings in the annular member 22 and between the vanes 23. The bolts 29 are secured to the flange 21 of the mounting ring 18. Thus the front plate- The furnace wall is provided with an.

The member 22 carries a plurality of vanes. 23 which may be suitably secured thereto by welding or in 27 is held in rigid assembled relationship with respect to the annular member 22 and the mounting ring 18.

The front plate 27 is provided with a large central opening 31 which is closed by a disc-shaped member 32. The member 32 is maintained in a position closing the opening 31 by means of cap screws 33 which extend through ears 34 carried at circumferentially spaced points about the periphery of the disc-shaped member 32. The cap screws 33 engage threaded openings (not shown) in the front plate 27. An aperture 36 is provided in the central portion of the disc-shaped member 32. A boss 37 is integral with the disc member and extends outwardly therefrom as shown in Fig. 2. The aperture 36 accommodates a tube 38 which extends axially of the air control mechanism and terminates at its inner end adjacent the burner 17. The tube 38 provides guide means for a contoured air shutter as hereinafter described and also encases a portion of a fuel supply conduit 39 for the burner. It will be appreciated that the conduit 39 or other suitable means may extend through the outer end of the tube 38 for connection to a fuel supply.

The disc-shaped member 32 is provided with an opening 41 for receiving a short pipe 42. The pipe 42 is secured in position within the opening 41 and extends inwardly and terminates in an open end 43. The outer end of the pipe 42 is normally covered by a suitable transparent window 44 carried by a frame 46. The frame 46 is mounted for swinging movement about a pivot 47. The pipe 42 serves the purpose of permitting the fuel at the burner 17 to be ignited by a lighting torch or the like introduced through the pipe 42 when the window frame 46 is swung to a position uncovering the outer end of the pipe. The transparent cover serves as a peep hole for observation of the flame conditions prevailing forwardly of the burner 17.

A contoured air shutter 48 is mounted for sliding movement on the tube 38. The air shutter is provided with a sleeve portion 49 which surrounds the tube 38 and prevents tilting of the air shutter on the tube. The sleeve portion 49 fits snugly on the tube 38 and guides the shutter as the sleeve slides on the tube. The air shutter is provided with an aperture 51 for receiving the inner end of the pipe 42. The outer peripheral portion 52 of the air shutter is preferably arranged in a common plane and an annular concave part 53 connects the inner portion with the peripheral portion 52. This annular concave surface is provided for deflecting the air entering at the periphery of the shutter axially of the tip of the burner 17.

A pair of handles 56 and 57 are mounted outwardly of v the disc-shaped member 32. A rod 58 (Fig. is secured to the handle 56 and a rod 59 is attached to the handle 57. The inner ends of the rods 58 and 59 are secured to the air shutter 48. Thus the air shutter 48 may be moved from its extreme inward position illustrated in Fig. 2 to an outermost position where the peripheral portion 52 engages the inner surface of the disc member 32. It is to be noted that the diameter of the air shutter 48 is slightly less than the diameter of the opening 31 in the annular front plate 27.

Another element of the invention pertains to a ringshaped baflle member 61 which is in the form of a relatively short cylinder and having a slightly larger diameter than the annular member 22. The baflle member 61 may be regarded as a splitter damper" and is adapted to be moved in two directions as represented by the double arrow 62 in Fig. 2. The damper ring 61 may be moved by handles 63 and 64. These handles are secured respectively to the outer end of rods 66 and 67 which extend through openings in the front plate 27. The inner ends of the rods 66 and 67 may be secured to ears 69 and 71. Thus the damper ring 61 may be moved inwardly and outwardly beyond the positions shown in Fig. 2 by applying pushing or pulling forces to the handles 63 and 64. The

damper ring 61 is impervious throughout its circumference and acts as a bafle to prevent radial inward movement of the air except over both ends or one end thereof.

In operation the burner 17 is ignited and the contoured air shutter 48 may be moved to its outermost position by pulling on the handles 56 and 57. The peripheral portion 52 of the air shutter will then lie in the same plane as the front plate 27. If it is desired to provide maximum rotation of the incoming air the baflle ring 61 may also be moved to its outermost position so that the end 73 abuts against the inner face of the front plate 27. The secondary air must then enter through the spaces between the vanes 23. All of the incoming air will thereby be moved circumferentially so that its tangential component is at a maximum. The rotating or whirling air then moves into the presence of the fuel being burned forwardly of the burner 17 and a flame somewhat of the type as indicated at 74 in Fig. 7 is produced.

If an elongated flame is desired the damper ring 61 is moved to its innermost position by pushing on the handles 63 and 64 until the end 76 of the damper ring engages the mounting ring 18. The secondary air is thereby prevented from moving radially inwardly between the vanes 23 and all of the secondary air will move through the annular space between the end 73 of the damper ring and the air shutter 48. The incoming air under such circumstances will not be rotated but flows generally radially inwardly and is thereafter diverted axially by the annular concave surface 53 of the contoured air shutter 48. A flame somewhat of the shape shown at 76 in Fig. 6 is produced when no spin is imparted to the secondary air.

Other operating conditions may be obtained by positioning the baifle ring 61 in positions intermediate of its extreme forward and rear positions. The damper ring 61 may be located as shown in Fig. 2. When the air shutter 48 is also in the position shown in Fig. 2 the only secondary air admitted to the presence of the burner will flow through portions of the vanes 23 and secondary air will be moved circumferentially to a maximum extent. When the air shutter 48 is in the position shown in Fig. 2 air entering between the end 73 of the damper ring 61 and the front plate 27 does not move into the presence of the fuel being burned. It is possible to move the air shutter 48 to its outermost position with the damper ring 61 remaining in the position shown in Fig. 2. Under such circumstances a portion of the incoming air will be rotated by the vanes 23 and the other portion entering between the end 73 of the damper ring and the front plate 27 will move radially inwardly without being caused to move in a circumferential direction. The mechanism thus makes it possible to vary the relative quantities of air which is spinning rapidly and the air which is not spinning from one hundred per cent spinning to zero spinning. In other words it is possible to obtain any condition of combined air rotation between full spin and no spin. Accordingly any flame condition between the widespread pattern of Fig. 7 and the elongated flame of Fig. 6 can be obtained. When the air shutter 48 is in its outermost position the cross sectional area for the incoming air is of the same proportions regardless of the position of the damper ring 61. Accordingly there will be no appreciable air pressure drop for a given volume of the incoming air regardless of the spin or lack of spin imparted to the secondary air. Accordingly the disadvantageous conditions developed by tilting louvers are avoided.

While the invention has been shown and described with reference to particular structural features it will be appreciated that changes may be made in the details as well as the general organization. Such modifications and others may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

What we claim and desire to secure by Letters Patent 1. An air control mechanism for a fuel burner comprising, a mounting ring adapted to be secured to a furnace, an annular member positioned outwardly of the mounting ring, a plurality of circumferentially spaced vanes rigidly secured to the annular member and disposed in chord positions relative to the annular member, a front plate spaced outwardly from said annular member providing an annular opening outwardly beyond said vanes, means securing the front plate and the annular member to said mounting ring, a tube supported axially of the annular member, a contoured air shutter slidably mounted on said tube, a peripheral portion on said shutter arranged substantially at right angles to the axis of said tube and connected by a concave wall to an inner portion of the shutter, said shutter having a diameter slightly less than the annular member so as to be movable from a position adjacent the front plate to a position adjacent outer ends of the vanes, and a baffie member surrounding the annular member movable axially of said tube between the mounting ring and the front plate to overlie said vanes or said annular opening or to overlie 2 portions of said vanes and a portion of said annular opening.

2. In a control mechanism for a fuel burner, a mounting ring adapted to be mounted on a Wall of a furnace, an annular member positioned outwardly of the mounting ring, a plurality of circumferentially spaced vanes carried by the annular member and disposed in fixed chord positions relative to the annular member, a ringshaped front plate spaced outwardly from said annular member, means securing the front plate and the annular member to said mounting ring, second means closing a central opening in said second means, a tube supported by the front plate and extending axially of the annular member, a contoured air shutter member slidably mounted on said tube, said air shutter having a peripheral por tion of slightly less diameter than said annular member and disposed generally transversely of said tube and movable between the second means and said mounting ring, a baffle ring surrounding the annular member movable axially of said tube between the mounting ring and the front plate, and said baffle ring having a dimension substantially equal to the length of said vanes.

References Cited in the file of this patent UNITED STATES PATENTS 1,177,028 Fischer Mar. 28, 1916 1,329,279 Voorheis Ian. 27, 1920 1,380,739 Reid June 7, 1921 1,651,348 Bixby Nov. 29, 1927 1,878,926 Yarrow Sept. 20, 1932 1,966,524 Schenck July 17, 1934 FOREIGN PATENTS 597,170 France Aug. 22, 1925 

